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Summary Within the chromosome of the archaebacterium Sulfolobus sp. B12, a 7.4 kb region was identified which displayed extensive sequence similarities to the 15.5 kb genetic element SSV1 carried by the same strain both as a circular form and as a site-specifically integrated copy. DNA sequence analysis indicated that this 7.4 kb region (designated SSV1intB) represented an SSV1-like element distinguishable from the full-length integrated copy (designated SSV1intA) by extensive deletions and point mutations. The physical organization of DNA sequences of SSV1intB indicated that this element was integrated at the same attP site as previously identified for SSV1intA. A comparison of the DNA sequences at the left attachment sites of SSV1intA and SSV1intB revealed that they both represented very similar putative arginine tRNA genes followed by a 10 by inverted repeat sequence. S1 nuclease mapping experiments indicated that these tRNA genes are transcribed.
Offprint requests to: W. Zillig 相似文献
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It is possible to replace the CaMV (cauliflower mosaic virus) ORF (open reading frame) II with foreign sequences without interfering with virus viability. Such recom-binants can induce the synthesis of substantial amounts of a foreign protein in infected plants and confer new properties to these plants. However, so far only three genes have been successfully cloned and expressed in this way. The expression mechanism of CaMV demands precise replacement of ORF II and probably certain structural features of the viral 35S RNA, which should not be disturbed by inserted sequences. Since these features are largely unknown, it cannot at present be pre-dicted whether an insert will be tolerated. It is more likely that larger inserts will disturb the viral gene expression mechanism than smaller ones. 相似文献
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The present study was undertaken to investigate the role of calcium ions (Ca2+) in the induction and secretion of the dengue type 2 virus induced cytotoxic factor and the cytotoxin. This was done by using
calcium channel blocking drugs such as verapamil, nifedipine or diltiazem hydrochloride. The production of cytotoxic factor
was significantly reduced by treatment of dengue type 2 virus infected mice with verapamil. Similarly, a dosedependent inhibition
of the secretion of cytotoxic factor was observed, when spleen cells of the virus-primed mice were treatedin vitro with the 3 calcium channel blockers. The production of cytotoxin by macrophages was abrogated by pretreatment with calcium
channel blockers but had little effect on its secretion as shown by treatment of macrophages with verapamil at 1 h after the
induction to later periods up to 18 h. The findings thus show that in the induction of both the cytokines Ca2+ plays a critical role; on the other hand it is required for the secretion of the cytotoxic factor but not for that of the
cytotoxin. 相似文献
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